First, Maddux was convinced no hitter could tell the speed of a
pitch with any meaningful accuracy. To demonstrate, he pointed at
a road a quarter-mile away and said it was impossible to tell if a
car was going 55, 65 or 75 mph unless there was another car nearby
to offer a point of reference.

“You just can’t do it,” he said. Sometimes hitters can pick up
differences in spin. They can identify pitches if there are
different releases points or if a curveball starts with an upward
hump as it leaves the pitcher’s hand. But if a pitcher can change
speeds, every hitter is helpless, limited by human vision.